"I wanted to make something simple, from natural materials, without concrete and extra costs. I believe that in the 21st Century houses can also be made using this eternal technology – from stone, wood, wattle and clay. The house does not have its own roof because of the complete freedom I needed to work with these materials and follow this technology." Everything in this unique home is handmade.

Will he continue to produce habitable sculptures? "No, I am no longer interested in this; it is like a trodden path for me. I am happy that I did something large-scale. I am proud not so much of the form – there are infinite possibilities, but of the innovative idea. I had been working on it for a long time and I knew that no such thing had been done anywhere else.

There is no modesty in Koychev's words for a simple reason – the idea of making a sculpture of wattle and mud had been in his mind since the beginning of the 1990s. Back then, he was sure he was on the right track – the materials were cheap and malleable, allowing for bold decisions regarding size, and loaded with symbolism. This is how The Dung Beetle appeared in 1994. 

Nine enormous baskets of interwoven stakes and manure sprouted in the green areas around the National Palace of Culture, looking like structures created by nature. When criticised that the composition was too delicate and would be washed away by heavy rain, Koychev replied that if it was good enough, it would remain in the minds of the public. This was obviously not enough for some people; seven of the pieces of what was one of the first art installations in post-Communist Bulgaria disappeared without a trace.

Koychev's concept of a sculpture that you can also view from the inside was central for Obitalishteto, or the Abode, a joint project with architect Boyko Kadinov. The six by 10 m structure of wood, straw and manure resembling a stable or a womb with steel legs enticed visitors to enter and sit inside it. As is always the case with Koychev's work, the installation was in complete harmony with the place where it was displayed, in front of the Archaeological Museum and the Presidency in Sofia. The Abode also travelled to Brussels for the Europalia Festival in 2002.

What came next was something completely different – models of colourful houses made from stone, wood and adobe. In the exhibition entitled Houses, Summer, the Sea: An Idea of a Holiday Village, the models were displayed against a background of photographs by Ivo Hadzhimishev, which showed still undeveloped corners on the Bulgarian Black Sea coast, such as Kamen Bryag in the north.

"Everything I do is a commentary on what I see," Koychev says of his work. His critical attitude to modern man's transgressions against nature is not devoid of irony. The first part of the composition of Artificialities. Something about Cloning, an open-air installation in Osikovitsa, uses real cows, sheep and visitors, while the second consists of plywood models of cows, sheep and people. In The Herd, large black bulls wade in a specially made mud puddle in front of a glitzy hotel in Sunny Beach. In A Haughty Walk, six five-metre male and female Styrofoam figures soar above a veil of foliage, their fronts clad in the latest fashions and their backs naked.

A mountain climber and one of the first to go camping with a tent in Communist Bulgaria, Koychev has a special affinity with nature and often chooses to show his work in the open air. "I find it more interesting there – you have to decide how to step into this space and what to do, having in mind that any human activity has an adverse effect outside the house."

In this respect, New York was a real revelation: "The city has been created with a flair for the monumental; you don't get to think of its large scale – it is natural."  Koychev was last there in 1999 on a Studio International Programme. He took part in the World Artists at the Millennium Exhibition, staged in the UN building, together with 36 other artists aged over 60, including Louise Bourgeois, Ilya Kabakov and Kenneth Noland.